Raman analysis of aqueous solutions of ethylene glycol and 1,3-propylene glycol: Fundamental and applied aspects.

Aqueous solutions of glycols, on the one hand, are widely used in many applications; on the other hand, they can serve as simple and representative models for studying intra- and intermolecular hydrogen bonds. In this work, we analyze the possibilities and limitations of Raman spectroscopy for fundamental and applied researches of such solutions on the examples of ethylene glycol (EG) and 1,3-propylene glycol (1,3-PG). It is shown that Raman spectroscopy is an effective tool for monitoring temporal changes in the structure of glycol solutions deposited on substrates. This study demonstrates that the water content in the solutions on the substrates decreases rapidly with time, and the rate of this decrease depends on the chemical structure of both glycol and substrate. It was found that the reduction in the water content leads to slight decrease in the contents of gauche-conformers in the backbones of EG and 1,3-PG molecules. It is shown that use of the 1064 nm excitation ensures a reliable Raman analysis of automotive antifreezes containing various dyes, in particular determination of the relative contents of water and glycol.

Raman evaluation of the crystallinity degree and composition of poly(L-lactide-co-ε-caprolactone).

In this work, we study two series of the copolymers of L-lactide (LLA) and ε-caprolactone (CL) with the CL molar content of 5, 15, and 30 %. The first series was the commercial semicrystalline granules (Corbion, Netherlands), which we analyzed without any additional modification. The second series was amorphous films, prepared from the granules by hot pressing with the subsequent fast quenching in order to avoid the crystallization. We used Raman spectroscopy in conjunction with the quantum chemical modeling to evaluate the structure of the copolymers. As additional methods, we applied X-ray diffraction (XRD) analysis and differential scanning calorimetry (DSC). The main result of our study is the elaboration of the Raman methods of quantitative analysis of the relative contents of the comonomers and the crystallinity degree of the poly(L-lactide-co-ε-caprolactone). These methods are based on measurements of the ratios of the peak intensities of the poly(L-lactide) (PLLA) bands at 411 and 874 cm-1, the PLLA band at 2947 cm-1 and the poly(ε-caprolactone) band at 2914 cm-1. Raman study shows that growth of the CL content causes the monotonous decrease in the crystallinity degree of PLLA blocks. Density functional theory analysis of LLA decamer in the conformation of helix 103 allows us to assign the PLLA Raman bands. The Raman data on the composition and crystallinity degree of the copolymers correlate very well with the results of XRD and DSC studies, as well as with the information on the composition of the copolymers provided by manufacturer.

Raman structural study of ethylene glycol and 1,3-propylene glycol aqueous solutions.

Raman spectra of ethylene glycol (EG) and 1,3-propylene glycol (1,3-PG) aqueous solutions with the diol content from 10 to 90 mol% were measured. The diol content weakly influences the EG and 1,3-PG Raman bands in the spectra of the solutions in the region 250-1800 cm-1. This fact means that the conformational compositions of both the diols do not change significantly with dissolving in water. The intensity of the OH stretching band with respect to the diol bands intensities is the linear function of the ratio of the mole contents of water and the diol in the solutions. The spectral region 2800-3800 cm-1 can be used to evaluate the chemical composition of these binary solutions. DFT modeling of the Raman spectra of EG molecule in water shell confirms the prevalence of the gauche-conformation of EG in the aqueous solutions.

Relations between the Raman spectra and molecular structure of selected carotenoids: DFT study of α-carotene, ß-carotene, γ-carotene and lycopene.

Using the density functional theory (DFT), we calculated the structures and Raman spectra of trans-isomers of α-carotene, ß-carotene, γ-carotene and lycopene as well as trans-isomers of modified ß-carotene and lycopene molecules with substituted end or/and side groups. The DFT calculations showed that the position of the CC stretching band depends mainly on the number of conjugated CC bonds and decreases with an increase in the conjugation length. The weak dependence of the position of the CC stretching band on the structure of the carotenoid side and end groups suggests that this band can be used to evaluate the conjugation length for trans-isomers of various molecules containing polyene chains. The CC stretching band shifts towards lower wavenumbers with growth of the conjugation length or masses of the end groups and to higher wavenumbers in the presence of the side CH3 groups. The intensities of the CC and CC stretching bands are enhanced with growth of the conjugation length or masses of the end groups. The presence of the side CH3 groups results in bending of the carotenoid backbone, splitting and dumping of intensities of the CC and CC stretching bands.

DFT study of Raman spectra of polyenes and ß-carotene: Dependence on length of polyene chain and isomer type.

We carried out calculations of non-resonance Raman spectra of ß-carotene and polyenes CH2(CHCH)n-2CHCH2 using the density functional theory (DFT). We revealed that the peak positions and intensities of the CC and CC stretching bands depend on length of the polyene chain and type of the isomer. Our experimental non-resonance Raman spectra of ß-carotene powder match well the DFT-simulated Raman spectrum of ß-carotene in the all-trans form. The peak positions and relative intensities of the CC and CC stretching bands of ß-carotene turned out to be similar in the resonance and non-resonance Raman spectra. An increase in the number of conjugated double bonds (n = 3-30) in a polyene structure results in a monotonous shift of the positions of the most intense CC and CC bands towards lower wavenumbers with an increase in the band intensities. An increase in the isomer number results in the monotonous decrease of the CC stretching band intensity for polyenes with 9, 10, 11, 15 and 24 double bonds. An increase in the isomer number inhomogeneously influences the form, position and intensity of the CC stretching band.

[Mechanisms of extreme states in human]. / Mekhanizmy razvitiia ékstremal'nykh sostoianii cheloveka.

Pathogenesis of extreme states during hypoxic hypoxia, exogenic and combined hyperthermia, aerial and immersion hypothermia is mainly associated with deterioration of reactivity and decline of functional reserves of the neuroendocrinal system, energetic dysbalance against more pronounced signs of anaerobic catabolism and recruitment of plastic resources of the body, activation of peroxide oxidation of lipids (POL), depletion of AOS potential with labilization of cellular membranes, and progressing changes in structural and functional relations within the antigenous/structural homeostasis. The determinacy of extreme state is influenced by initial status of the body functioning. The bodily extreme state has been found to depend on severity of asthenisation, peculiarities of the autonomous regulation, metabolic and immune status. Partial or full reversibility of decompensation disorders distinguishes extreme state from the critical (predeterminal) one. The relative adequacy of compensation and the principal possibility of a beneficial result are the necessary conditions for extreme state verification. Otherwise, in the lack of time for effective compensation typical syndromes of critical states may develop already during acute adaptation. There can develop partial insufficiency of a dominating functional system which will be compensated at the sacrifice of other organs and tissues. Sometimes extreme state may result in development of marginal or pathological states with human living activities preserved.

[The mechanisms of central regulation disorder under combat exposure conditions]. / Mekhanizmy narusheniia tsentral'noi reguliatsii v usloviiakh boevykh deistvii.

Results of research in central regulation system's disorders in the local wars' participants suffering from environmental psychoemotional and traumatic stress. It has been established, that there was an upsetting of interaction between neurodynamic processes in the sub-dominant hemisphere and a reduction of the functional reserve of the brain. Neurophysiology disorders discovered come from the pathological system that had been formed up in the central nervous system preserve their persistence for several years after the war.

[Clinical-physiological aspects of normobaric hypoxic training effects on functional status of patients with neurocirculatory dystonia]. / Kliniko-fiziologicheskie aspekty vliianiia normobaricheskoi gipoksicheskoi trenirovki na funktsional'noe sostoianie bol'nykh neirotsirkuliatornoi distoniei.

Profiles of external respiration and circulation, self-assessment of health, mental performance, sensory functions, and peripheral blood were studied in patients with neurocirculatory dystonia in the course of normobaric hypoxic training. The hypoxic training proved to successfully normalize arterial pressure, eliminate cardiac arrhythmias, and benefit general condition. Substantial strengthening of hypoxic resistance was stated along with an oxygen debt reduction during hypoxia, improvement of sensory coordination and mental performance, and activation of erythropoiesis.

[Psychophysiological support for the professional activities of servicemen]. / Psikhofiziologicheskoe obespechenie professional'noi deiatel'nosti voennosluzhashchikh.

Optimal solution of the personnel replenishment problem, the necessity of training and education process improvement in the training centers and schools, the outcome of social, psychological and medical measures greatly depend on the overall physical and mental health state of the servicemen and their professional training quality. On the basis of their long standing experience the authors discuss the traits of the psychophysiological maintenance of the military professional activities of servicemen, in particular--the methodology and theory of professional psychological selection, the importance of body functional indications for the estimation of the fighting capabilities of military units. They examine some prospects for the psychophysiological expertise in the promotion procedures of commanding officers and make a suggestion that psychophysiological maintenance in the Armed Forces would increase its combat capabilities and help to avoid some negative effects in military groups.

[Changes in the work capacity of the operators of command-measuring systems during daily duty]. / Izmenenie rabotosposobnosti operatorov komandno-izmeritel'nykh kompleksov v protsesse sutochnogo dezhurstva.

Through 12 hours of work the operators of command-measuring complexes had initial signs of exhaustion, showed them-self by decrease of health state, activity, mood, increase of latent period of simple sensorimotor reaction. These changes of a functional condition had no effect on quality of fulfillment of target problems. At the end of daily duty exhaustion, described by deterioration of health state, increase of operators' anxiousness, rapid pulse, reduction of time of delay of breath, increase of time of instability of sensorimotor reactions, amount of faulty actions, reduction of speed of mental processes and distribution of attention were developed.